Heating apparatus for material in strip form

ABSTRACT

A machine for use in bonding corrugated cardboard includes a heated plate over which the material to be bonded is fed. To vary the temperature to which the material is heated, means are provided for adjusting the vertical spacing between the material and the upper surface of the plate. Said means comprises a fan for blowing a gas through openings in the plate to lift the material above the plate.

United States Patent [191 Wittstock et al.

[4 1 Jan. 21, 1975 HEATING APPARATUS FOR MATERIAL IN STRIP FORM Inventors: Gerhard Wittstock, Pinneberg;

Walter Hoimeister, Ulzburg, both of Germany Assignee: Werner H.K. Peters Maschinenfabrik G.m.b.H.,

Hamburg, Germany Filed: Oct. 17, 1973 Appl. No.1 407,075

Related U.S. Application Data Continuation-in-part of Ser. No. 279,022, Aug. 9,

1972, abandoned.

Foreign Application Priority Data Apr. 13, 1972 Germany 2217833 U.S. Cl 34/54, 34/156, 34/162,

References Cited UNITED STATES PATENTS 12/1910 Taylor 34/152 995,084 6/1911 Pacyna 34/152 1,310,511 7/1919 Summers 34/32 2,236,056 3/1941 Grimm 34/155 2,252,585 8/1941 Swanson et al 34/162 2,306,607 12/1942 Horton 34/32 3,175,300 3/1965 Nitchie 34/156 3,217,425 11/1965 Nikkel 34/54 3,319,353 5/1967 Matsunami et al. 34/162 3,368,933 2/1968 Wicker 34/162 FOREIGN PATENTS OR APPLICATIONS 1,088,794 9/1960 Germany 34/18 Primary ExaminerCharles J. Myhre Assistant ExaminerPau1 Devinsky Attorney, Agent, or Firm-Beaman & Beaman [57] ABSTRACT A machine for use in bonding corrugated cardboard includes a heated plate over which the material to be bonded is fed. To vary the temperature to which the material is heated, means are provided for adjusting the vertical spacing between the material and the upper surface of the plate. Said means comprises a fan for blowing a gas through openings in the plate to lift the material above the plate.

6 Claims, 6 Drawing Figures I r I ll I ll "NJ" 11 0c ua va ue I 7 I I set point servo deviation PAIENIEB 3.861.057

SHEET 10F 2 Fig. 1

5 5- 3 actual value Pmmanmz I915 3.861.057

SHEET 20F 2 Fig.4

Fig.5 j 22 l 43 in! point 44 deyiai/on i5 acfual value HEATING APPARATUS FOR MATERIAL IN STRIP FORM CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part application of ser. No. 279,022 filed Aug. 9, 1972, now abandoned.

BACKGROUND OF THE INVENTION The invention relates to heating apparatus for material in strip form, especially to such apparatus in a machine for bonding corrugated cardboard, having at least one heating plate over which the material in strip form is fed in close proximity of the heating surface of the heating plate, and a temperature-regulating device by means of which the temperature of the material is vairied.

In the case of existing machines for bonding corrugated carboard, the strips of cardboard are fed one after another over a number of heating plates and are heated by them. the degree of heating depends upon the moisture content of the cardboard, the conveyor speed, the thickness of the cardboard and other factors, so that the maintenance of a pre-selected constant temperature gives rise to considerable difficulties, since in particular the conveyor speed and the mositure content of the cardboard may vary continuously during operation. Special difficulties arise if the running speed of the cardboard is fixed at zero or close to zero when joining the end of one strip to the beginning of another strip. In such a case, the cardboard is subjected to overheating and there is a danger that large lengths of strip may be made unusable and unsuitable for further treatment.

A machine for bonding corrugated cardboard is already known in which temperature regulation, particu larly when joining one strip to another, is achieved by making the heating plate adjustable, so that by means of a suitable adjusting device the plate can be lowered to a greater or lesser degree from the cardboard strip. However, such an arrangement is extremely expensive. A further disadvantage is that, when the heating plate is shifted, the individual strips of the corrugated cardboard can no longer be presseed against one another. Also, there is a danger that the lower smooth strip, in particular, may come apart from the corrugated strip.

Another machine for bonding corrugated cardboard is known in which temperature regulation is obtained through vents arranged between two neighbouring heating plates which blow cool air on to the corrugated cardboard strip. It is, however, still not possible to prevent certain parts of the cardboard strip being overheated by the heating plate.

Finally, a machine for bonding corrugated cardboard is known in which the cardboard strip is held on the heating surface of the heating plate by means of air pressure. A certain amount of cooling is, indeed, effected in this way but this is not enough if the corrugated cardboard strip is moved at too low a speed.

It is indeed possible to make the temperature of the heating plate itself variable. However, by reason of the relatively high heat capacity of this type of heating plate, temperature variation can only be effeced over lengthy periods, which are usually too long to prevent excessive heating of the corrugated cardboard.

Prior art patents pertinent to the field of the invention are represented by US. Pat. Nos. 2,941,573, 3,472,158, and German Pat. No. 2,037,441.

SUMMARY OF THE INVENTION The object of the invention is to produce a heating apparatus for strip material especially in a machine for bonding corrugated cardboard, which makes it possible to prevent the material from being overheated by the heating plate.

The invention comprises fitting a lifting means to the heating plate by means of which the strip material can be raised above the heating surface of the heating plate. Thus, the strip material, while being raised above the heating surface, is heated less strongly by the heating plate and its temperature is momentarily lowered. In this manner, the danger of oveheating the material, for example corrugated cardboard, is effectively avoided.

The lifting means advantageously comprises a blowing apparatus by which a cooling gaseous medium can beblown between the heating plate and the raised strip material. With the help of the cooling medium, an additional influence on the temperature of the strip material is obtained in the area of the heating plate. At least one outlet opening may be provided in the heating surface of the heating plate, the opening being connected to the discharge point of a pressure source in order to create a builtup pressure between the heating surface and the strip material.

By creating an increased gas pressure between the heating surface of the heating plate and the strip material, it is possible to predeterrnine the distance between the heating surface and the material and thereby also to determine the extent of the effect of the heating plate on the material. The expenditure necessary to obtain this result is extremely small and exceptionally effective and rapid cooling of the material can be obtained. Within seconds the temperature can be reduced by up to 50 percent of that which would exist if there were no cooling. a further advantage is that, in a machine for bonding corrugated cardboard, as a result of the maintained pressure, the lower smooth strip is constantly held against the corrugated strip lying beneath It.

At least one adjustable stop may be disposed above the heating surface of the heating plate, against which the strip material is lifted by the creation of the increased gas pressure. The setting of the stop thus determines the maximum height to which the material can be raised above the heating surface. For example, with machines for bonding corrugatged cardboard, the strips of material are fed over the heating plate beneath the belt of a conveyor, whereby a load mechanism forces the belt and the strips toward the heating plate with a pre-selected pressure. The stop may thus be formed by a load mechanism having a preselected amount of play, which holds the strip material against the heating surface above a belt or equivalent part of a strip conveyor mechanism which carries the material underneath it. The load mechanism may consist of at least one load roller which is mounted so that it can be adjusted in a direction perpendicular to its axis and is capable of being brought in contact with the belt. It is possible, with the help of the sustained gas pressure, not only to lift up the strip material and the conveyor belt, but also the load roller which exerts a preselected downward pressure on both of them. For this, however, a relatively greater sustained gas pressure and a corresponding more powerful pressure source would be nec essary. An adjustable mechanism may accordingly be provided for the load roller which lifts it a prescribed distance above the heating surface, if a sustained pressure between the heating surface and the strip material in strip form is obtained. The sustained pressure needs only to be sufficiently large to lift the strip material and the belt a prescribed amount, while the load roller is adjusted independently of them with the help of the adjusting mechanism. The action of the adjusting mechanism is dependent on the application of the sustained pressure, which, in its turn, is made to depend upon factors which are explained below.

The lifting mechanism may comprise a plate which conducts heat, is located above the surface of the heating plate yet capable of being brought in contact with it, and over which the material in strip form is carried so that it can be lifted above the heating surface. The plate forms a heating surface which can be lifted off the heating plate and cools down momentarily after being lifted, so that the material in strip form can also cool. In another variation, a gas pressure is built up beneath the plate and the plate has a downwardly projecting rim which prevents the pressure escaping to the side. The plate with the downwardly projecting rim acts like a piston which can be raised by said pressure. The downwardly projecting rim supports the build-up of a pressure cushion.

One or more round or slot-shaped openings may be formed in the heating plate, for example, several parallel slot-shaped openings can be provided. Each opening may be connected with a reservoir arranged on the side of the heating plate opposite the heating surface and connected with the pressure source. The reservoir is thereby bounded by the underneath side of the heating plate. Various gaseous substances can be used as the media for building up a sustained pressure. For example, air can be used. In this connection, the reservoir may be connected to the discharge side of one or several fans. In general, a single fan is sufficient to build up the necessary sustained pressure; it is arranged directly beneath the reservoir container and blows air into it.

In order to suit the desired operational requirements and to obtain the desired temperature of the strip material, the quantity of the pressure medium conveyed from its source to the opening can be variable. On the one hand the spacing between the heating plate and the strip material and on the other hand the cooling effect achieved by the build-up of the pressure cushion in said space are made variable.

For many applications, it is desirable to provide additional means which will enable the temperature of the strip material to be changed more quickly than can be achieved by a change in the temperature of the heating plate itself. A moistening arrangement may accordingly be provided by means of which the temperature of the gas can be brought to prescribed variable levels. In this way, the cooling effect of the gas cushion upon the raised strip material is varied.

In many cases, as for example corrugated cardboard, the material in strip form contains a definite amount of moisture. The moisture content of the cardboard determines to a considerable extent the maximum permissible rate of heating. A moistening device may accordingly be provided by which the moisture content of the gas can be maintained at a prescribed level. In this connection, it is proposed that the heating arrangement should be linked with a water injector through which water can be sprayed into the gas in order to maintain the temperature and moisture content of the gas at the required values. In this connection, it is advantageous if a directing or regulating device determines the moisture content and/or temperature of the gas in accor' dance with the load on the heating plate. It is thus possible in a simple manner to maintain the temperature and moisture content of the strip material at desired levels. This is particularly important with machines for bonding corrugated cardboard. A further version provides for the loading of the heating plate to be determined by the temperature of the heating plate and/or the strip speed and/or the quality of the strip material. Sensors may be provided which record the above factors and accordingly activate the directing or regulating device.

If a fan is used as the source of the pressure, a filter may be fitted in the suction channel of the ventilator. A noise suppressor may be provided in the intake of the fan.

BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described in more detail by way of two examples of embodiment.

In the drawings,

FIG. 1 shows a side view of a heating device of a machine for fabricating corrugated cardboard,

FIG. 2 shows a sectional view taken on line 2--2 of the arrangement of FIG. 1,

FIG. 3 shows a sectional view taken on line 3-3 of the arrangement shown in FIG. 2,

FIG. 4 shows a top plan view taken of a heating plate of the arrangement according to FIG. 1,

FIG. 5 shows a detail of the arrangement according to FIGS. 1 and 2, and

FIG. 6 shows a schematic view of another example of embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the diagrammatic representation of the corrugated cardboard bonding machine according to FIG. 1 there are several heating plates 1 arranged a stationary machine stand 20. A transport belt 3 is arranged above the hot plates 1, said belt being turned via a roll 25 at the left-hand end in FIG. 1. The belt 3 is driven by a driving motor (not shown) and is guided above the heating faces of the heating plates 1 by rollers 4. The construction of the heating plates 1 and the manner of heating them will be dealt with in more detail further below. The corrugated cardboard strip 2 which is to be treated is supplied from the right between the belt 3 and another belt 27 which is tumed via a roll 26. A drying of the corrugated cardboard strip is effected with the aid of the individual heating plates 1, said corrugated cardboard strip having been provided before with a glue between the individual layers. The process step shown here for the production of corrugated cardboard is generally known and does not belong to the subject matter of the invention.

As may be best seen from FIG. 3, each heating plate 1 consists of several square tubes in side-by-side arrangement which are rigidly connected with each other, for instance, by welding. The square tubes are connected with each other at the ends thereof in such a manner that they form a continuous channel which (please see FIG. I) is connected with a heating line 24 and through which heating steam is supplied to the individual heating plates 1. It is also generally known per se to heat heating plates for corrugated cardboard bonding machines with steam.

As may be seen from FIG. 3, and also from FIG. 4, each heating plate 1 is provided with two longitudinally extending slots 5 which terminate upwardly in the upper heating face and terminate downwardly in a collecting chamber 8 which is defined by a sheathing formed beneath the heating plate 1. The heating plate 1 is supported by means of two carriers 14 and 15 which are connected with the machine stand not shown in this FIG. A fan wheel 28 is arranged in the lower region of the collecting chamber 8 which is driven with the aid of an electromotor 7. The electromotor 7 is fed from a d.c. source which is connected to the terminals of the electromotor 7 via a switch 37. The switch 37 is actuated by means of a servo device 34 via a linkage 38. The servo device 34 may be any type of known driving device which is actuable dependent upon a servo deviation. The servo deviation is formed by the difference between actual value and preset value which is formed in the comparison 30 between actual value and preset value. The actual value signal is generated with the aid of a thermosensor 29 which senses the temperature of the corrugated cardboard strip 2 (please see FIG. 3) and transforms it into a corresponding signal. The preset value is supplied by any type of preset value selector (not shown). The servo device 34 actuates in addition a potentiometer 35 in the path of current to the electromotor 7 in dependence upon the servo deviation.

As may be seen from FIGS. 3 and 5, the belt 3 is urged in a direction towards the heating plate 1 with the aid of load rollers 4. The load rollers 4 are rotatably supported in slots 22 of a bearing block 17 with the aid of bearing journals 23 (FIG. 2). The bearing block 17 is vertically guided by means of a dovetail guide of the machine stand 20. A hydraulically actuable adjusting cylinder 21 comes into engagement at the bearing block 17. The load rollers 4 may therefore be lifted and lowered in common by means of the adjusting cylinder 21. Each one is in addition movable in a limited extent by itself in a vertical direction.

The device shown in FIGS. 1-5 operates as follows: In FIG. 1 the corrugated cardboard strip is transported through the machine from right to left and while being so transported is kept in close engagement with the heating faces of the individual heating plates 1 with the aid of the load rollers 4 and the belt 3. Now, it may happen that owing to too low a speed of the corrugated cardboard strip 2 or even a standstill thereof the corrugated cardboard strip 2 becomes too highly heated by the heating plates 1 which may damage or even destroy the corrugated cardboard strip 2. The increase in the temperature of the corrugated cardboard strip is sensed by the thermosensor 29. The latter transmits a signal corresponding to the sensed temperature value onto the preset value/actual value comparator 30 which also receives the preset value.

The difference resulting from the comparison between actual value and preset value is transmitted to the servo device 34 as servo deviation which thereupon closes the switch 37 and brings the potentiometer into a certain position. The voltage of the dc source 36 is now connected across the terminals of the electromotor 7 which causes the fan wheel 28 to move. The fan wheel 28 blows air along the arrows in the collecting chamber 8. From here the air passes over the longitudinal slots 5 thus leaving the heating plate and arrives below the corrugated cardboard strip 2. The air leaving the longitudinal slots 5 builds up an air cushion between the heating plate 1 and the corrugated cardboard strip 2, whereby the corrugated cardboard strip 2, the belt 3 and the load rollers 4 are lifted (as may be seen also in FIG. 3). As a result, the corrugated cardboard strip 2 is removed from the direct region of influence of the heating plate 1. In addition, the exhausted air is effective to cool the corrugated cardboard strip, so that overheating of the corrugated cardboard strip will no longer occur. As will be seen from FIG. 5, the load rollers 4 too may be lifted by the air cushion. Another possibility consists in that the load rollers 4 are lifted via the bearing block 17 with the aid of the adjusting cylinders 21, i.e., in dependence upon the actuation of the fan motor 7 by the servo means 34, if a lifting of the corrugated cardboard strip disposed above the heating face of the heating plate 1 is desired. In such instance the cylinders 21 are connected to pressurized medium control valves which are controlled by servo means 34.

From FIG. 2 it may be seen that a spraying nozzle 10 is arranged beside the fan motor 7 which may be connected to a source of pressurized water. It is possible with the aid of the spraying nozzle 10 to spray water into the air sucked in by the fan wheel, in order to moisten the air serving to lift and cool the corrugated cardboard strip which exits from the slots 5 in the heating face.

In the case of the second embodiment according to FIG. 6 only the heating plate 1 with the two longitudinal slots 5 is shown. The heating plate is designed and constructed in the same manner as are the heating plates according to the preceding figures; this applies likewise to all the remaining parts of the overall device. In this embodiment, a frame 40 is placed around the heating plate 1, with a thermal conductive plate 41 of small thickness extending therebetween. A fan wheel 42 (diagrammatically shown) is driven by a fan motor 43 which is actuated by a servo device 44 which in turn is supplied with a servo deviation signal of a preset value/actual value comparison 45. The mode of operation of the regulating device is the same as the one described in connection with FIG. 3. When the fan motor 43 is switched on, the fan wheel 42 blows air through the longitudinal slots 5 towards the heating face of the heating plate 1. An upset pressure builds up below the thermally well conductive plate 41, by which the plate 41 is lifted together with the frame 40, in order to lift the corrugated cardboard strip 2 which moves from right to left in FIG. 6 (as shown by the arrow). The lateral frame 40 prevents the air escaping quickly sideways. This embodiment therefore offers the advantage that very little air is necessary to lift the corrugated cardboard strip 2.

We claim:

1. Apparatus for drying a web of strip material such as corrugated cardboard having a width comprising, in combination, a heated plate having an upper heating surface over which the web to be dried passes and a width at least as great as the width of said web, passages defined in said plate intersecting said upper heating surface and disposed substantially throughout the width of said web, an energizable source of gaseous cooling medium communicating with said passages, the

energizing of said cooling medium source introducing sufficient gaseous cooling medium into said passages to lift the web away from said plate heating surface to cool the web, said heated plate including a lower surface, said passages comprising a plurality of openings defined in said heated plate intersecting said plate upper and lower surfaces, a reservoir chamber defined below said heated plate partially defined by said plate lower surface, said source of cooling medium communicating with said reservoir chamber introducing cooling medium into said chamber upon energization, control means sensing the temperature of said heated web, said control means controlling energization of said cooling medium source, and vertically movable web positioning means disposed above and spaced from said plate heating surface above the web engaging said web in opposed relationship with respect to said plate heating surface tending to maintain the web biased toward said heating surface, said web positioning means being vertically lifted upon the web being lifted away from said plate heated surface by said gaseous cooling medium.

2. Apparatus for drying a web of strip material as in claim 1 wherein said cooling medium source comprises a fan.

3. Apparatus for drying a web of strip material as in claim 1, humidity increasing means communicating with said source of gaseous cooling medium selectively increasing the humidity of the cooling medium lifting the web away from said heating surface.

4. Apparatus for drying a web of strip material as in claim 1, said web positioning means including a conveyor belt engaging the web, and at least one load roller disposed above said conveyor belt and engaging said belt, vertically adjustable bearing means rotatably supporting said roller permitting vertical displacement of said roller and belt toward and away from said heated plate.

5. Apparatus for drying a web of strip material as in claim 1, wherein said heated plate includes a vertically movable heat conductive plate vertically movable with respect to said upper heating surface adapted to lift from said upper heating surface upon introduction of said gaseous cooling medium into said passages, said web engaging said vertically movable plate on the opposite side thereof with respect to said upper heating surface.

6. In an apparatus for drying a web of strip material as in claim 4, motor means connected to said bearing means for selectively vertically positioning said bearing means relative to said heated plate, control means sensing the temperature of said heated web, said control means controlling energization of said cooling medium source and said motor means. 

1. Apparatus for drying a web of strip material such as corrugated cardboard having a width comprising, in combination, a heated plate having an upper heating surface over which the web to be dried passes and a width at least as great as the width of said web, passages defined in said plate intersecting said upper heating surface and disposed substantially throughout the width of said web, an energizable source of gaseous cooling medium communicating with said passages, the energizing of said cooling medium source introducing sufficient gaseous cooling medium into said passages to lift the web away from said plate heating surface to cool the web, said heated plate including a lower surface, said passages comprising a plurality of openings defined in said heated plate intersecting said plate upper and lower surfaces, a reservoir chamber defined below said heated plate partially defined by said plate lower surface, said source of cooling medium communicating with said reservoir chamber introducing cooling medium into said chamber upon energization, control means sensing the temperature of said heated web, said control means controlling energization of said cooling medium source, and vertically movable web positioning means disposed above and spaced from said plate heating surface above the web engaging said web in opposed relationship with respect to said plate heating surface tending to maintain the web biased toward said heating surface, said web positioning means being vertically lifted upon the web being lifted away from said plate heated surface by said gaseous cooling medium.
 2. Apparatus for drying a web of strip material as in claim 1 wherein said cooling medium source comprises a fan.
 3. Apparatus for drying a web of strip material as in claim 1, humidity increasing means communicating with said source of gaseous cooling medium selectively increasing the humidity of the cooling medium lifting the web away from said heating surface.
 4. Apparatus for drying a web of strip material as in claim 1, said web positioning means including a conveyor belt engaging the web, and at least one load roller disposed above said conveyor belt and engaging said belt, vertically adjustable bearing means rotatably supporting said roller permitting vertical displacement of said roller and belt toward and away from said heated plate.
 5. Apparatus for drying a web of strip material as in claim 1, wherein said heated plate includes a vertically movable heat conductive plate vertically movable with respect to said upper heating surface adapted to lift from said upper heating surface upon introduction of said gaseous cooling medium into said passages, said web engaging said vertically movable plate on the opposite side thereof with respect to said upper heating surface.
 6. In an apparatus for drying a web of strip material as in claim 4, motor means connected to said bearing means for selectively vertically positioning said bearing means relative to said heated plate, control means sensing the temperature of said heated web, said control means controlling energization of said cooling medium source and said motor means. 